1. Field of the Invention
The present invention relates to a technology for moving a head on a storage medium to a predetermined destination position for retracting the head when a fall sensor detects a fall of a storage device.
2. Description of the Related Art
Recently, storage devices such as a magnetic disk drive are used as storage units of information terminal devices in many cases. For example, portable personal computers called laptop computers are widely used, and downsized magnetic disk drives are mounted on the laptop computers.
The magnetic disk drive is further downsized and is even mounted on a portable music reproducing device or a cellular phone. This is because the recording capacity of the magnetic disk drive is relatively large and the reading speed of recorded information has improved, and therefore the magnetic disk drive can be a relatively inexpensive high-performance storage unit.
Being portable, a laptop computer, a portable music reproducing device, and a cellular phone have a high probability of receiving shocks of falls. Meanwhile, the magnetic disk drive is very easily affected by the shocks of falls. For example, if a magnetic disk drive receives a shock when the magnetic head is reading and writing at the surface of the magnetic disk, the magnetic head may damage the surface of the magnetic disk. A problem of how to suppress damages of the magnetic disk due to falls arises when the magnetic disk drive is mounted on an information terminal device.
To avoid this problem, for example, Japanese Patent Application Laid-open No. 2002-8336 discloses a magnetic disk drive having a retraction mechanism that retracts a magnetic head from a magnetic disk surface when a fall detecting sensor detects a fall. The magnetic disk of this magnetic disk drive can avoid the magnetic head from physically damaging the magnetic disk upon falls.
However, conventional arts represented by Japanese Patent Application Laid-open No. 2002-8336 may significantly reduce efficiency of reading and writing processes of the magnetic disk since the conventional arts immediately retracts the magnetic head from the magnetic disk surface when a fall is detected and a retraction process is conducted even when a minor vibration is erroneously detected as a fall, therefore the magnetic head is frequently retracted from the magnetic disk surface.